'02 WR426 Issues?

I going to try this again.

I am a long time KTM rider. I need a second bike for numerous reasons. I have always liked the Yamaha thumpers, so I am going to buy one (I think). I have a line on a 2002 WR426 that I can get for $2500. It is in incredible condition, with extras, like O-ring, Ironman sprockets, Scott's ready, exc. It has a popping or hesitating during acceleration. It is YZ timed, has a new black box, and the carb has been gone through numerous times. It had this problem even before the YZ timing.

Here are my series of questions:

- did the '02-WR have any reported CAM problems (mis-ground)

- Any common electrical problems

- Any Valve train issues

- A few KTMs had the bottom part of the slide installed backwards that created issues - any Yamahas have this problem.

I do not want to become a frustrated Yamaha owner after years of owning KTM's, but I have always liked them and HAVE to give it a try.


I haven't heard of any problem with them.They are nice bikes and i would buy one for that price.If ya want i'll trade you a 2000 ktm 300mxc for it. :) The slide can be installed incorrectly on these bikes.Go to yamahas site to look at a parts fiche for correct installation.

I had a 2001 wr426 with what sounds like the same sort of problem. Mine was a small amount of dirt in the pilot jet. I took it apart twice and missed the very small restiction. It took a friend of mine to bail me out of that one. It just seems like most of the hestitaion misfires ect on these bikes are carb related. gook luck.

They are great bikes. I do not have that kind of problem with my 2002. I am sure it is carb. related. Try moving the needle down one clip. If it is on clip 4, move it to clip 3. This will get rid of any hesitation. Better yet, if it is uncorked, go to a jetting setup that is similar to mine - see sig.. Good Luck

to elaborate more, my bike will hesitate when gunning it off idle is the needle is set too rich. It does not pop. It just bogs, then catches and takes off. Leaning the needle, moving it down, fixes it. Find out what jetting and needle the bike is running and this will tell you more about the bike. Post your findings and we will try to help. :)

I posted this info. in my first thread regarding this misfire issue, but not in this one. I apologize for omitting this: A carb was taken off another bike and put on this one to see if that could be the problem. The bike STILL had the miss. The other bike ran perfectly.

I am probably going to go ahead and buy the bike anyway. I am willing to take the challenge, and it is an awesome deal. I just thought if a similar problem had been experienced by one or two of the thousands here it would save me MANY steps in diagnosis.

I would check that it is not sucking air at the manifold joins, also have a look at the bolt up flange of the header pipe and header to tailpipe join.

Strick, Go to Motomans site here on TT and read the YZ timing article. Then take a look. Very possible that the cams were not put back in properly.

For anyone interested. After a lengthy discussion with the previous owner of this WR regarding the mechanic that set up the YZ timing, I felt comfortable in believing it was performed correctly. The gray wire had also been cut, the throttle stop shortened and the BK mod installed. With, what I feel a strong jetting background, I decided to head in that direction.

I first checked the slide plate to make sure it was not installed upside down like some KTM's last year. I then installed a richer needle (OCEMP #3) - simple, quick try. I cold fouled the spark plug within 30 seconds. So, back to the drawing board. I decided just to remove the carb and check out the baseline settings and go from there. Stock needle (DRR #3) 45 pilot, 155 main, BK squirt ~ 2.5 seconds, mixture screw at 2 turns. I then realize I probably went the wrong direction with the needle clip position, and also quickly discerned the jetting was actually somewhat backwards. I change the needle (EMP) clip to #5, I take the mixture to 1 1/2 turns, I install a 38 pilot, 158 main, and time the BK squirt to what looks to be just under one second. Also one other interesting find. The spark plug was gapped like a KTM = .24. I installed a NEW plug at .30. I put in fresh gas, turn on the petcock, pull out the choke, give one full turn with the throttle, go one click past TDC with the kick starter, no luck. Once more - one click past TDC bring the kick starter back to the top, like before, and she purrs like a kitten (except I had the idle turned to high). I give the WR once (or four times) up the street and back, Man does this bike run. No surging, no back firing, just one heck of a pull. The head pipe did glow red when I was letting it idle and checking for any bog or backfire, but I hear that this is a normal occurrence with these bikes.

Thanks for all the responses. I just wanted to let everyone know the findings.


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